GB860202A - Improvements in or relating to vacuum braking systems - Google Patents

Abstract

860,202. Fluid-pressure brakes. CLAYTON DEWANDRE CO. Ltd. Nov. 13, 1959 [Aug. 13, 1958], No. 26033/58. Class 103 (1). A braking system includes a vacuum suspended servomotor having its cylinder extended to form a vacuum reservoir, the servomotor being controlled by valve means carried by the servo-piston and controlled mechanically by a pedal, the servo-piston thrust being transmitted by means disposed within the reservoir to a master cylinder. The extension 1a of cylinder 1, constituting the reservoir, houses the linkage 5, 6, 9 connecting piston 2 to master cylinder piston 10. A rod 3 is connected to a pedal and to a sleeve 15 fixed to a diaphragm 14 mounted in chamber 13 of piston 2. A boss 17 on piston 2, has a bore 19 connected via a flexible hose 18 to atmosphere and has a seat 20 normally engaged by a valve 22, a seat 23 formed on a sleeve 21 fixed to diaphragm 14, being normally spaced from valve 22. In the brake release position as shown, vacuum is communicated from reservoir 1a via port 24, past valve seat 23 and port 27 to the rear servomotor chamber and via port 28 to the chamber in front of diaphragm 14. On brake application, rod 3 moves diaphragm 14 and sleeves 15, 21 to the left to first engage seat 23 with valve 22 and then raise valve 22 from seat 20 to admit atmospheric pressure to the rear servomotor chamber via port 27 causing piston 2 to move and actuate the master cylinder. Atmosphere passes through port 28 to act on diaphragm 28 to oppose its movement to the left and so transmit " feel " to the pedal and operator. The follow-up movement of piston 2 establishes a lap position wherein valve 20 engages both seats 20, 23. On failure of the servomotor, movement of rod 3 eventually causes shoulder 29 on sleeve 15 to abut a stop 30 on a piston extension 16 to operate linkage 9, 6, 5 mechanically. In an alternative arrangement link 5 may be pivoted to the end wall 8 and link 6 to extension 16.